Author: Linda Chalker-Scott

Dr. Linda Chalker-Scott has a Ph.D. in Horticulture from Oregon State University and is an ISA certified arborist and an ASCA consulting arborist. She is WSU’s Extension Urban Horticulturist and a Professor in the Department of Horticulture, and holds two affiliate associate professor positions at University of Washington. She conducts research in applied plant and soil sciences, publishing the results in scientific articles and university Extension fact sheets. Linda also is the award-winning author of five books: the horticultural myth-busting The Informed Gardener (2008) and The Informed Gardener Blooms Again (2010) from the University of Washington Press and Sustainable Landscapes and Gardens: Good Science – Practical Application (2009) from GFG Publishing, Inc., and How Plants Work: The Science Behind the Amazing Things Plants Do from Timber Press (2015). Her latest effort is an update of Art Kruckeberg’s Gardening with Native Plants of the Pacific Northwest from UW Press (2019). In 2018 Linda was featured in a video series – The Science of Gardening – produced by The Great Courses. She also is one of the Garden Professors – a group of academic colleagues who educate and entertain through their blog and Facebook pages. Linda’s contribution to gardeners was recognized in 2017 by the Association for Garden Communicators as the first recipient of their Cynthia Westcott Scientific Writing Award. "The Garden Professors" Facebook page - www.facebook.com/TheGardenProfessors "The Garden Professors" Facebook group - www.facebook.com/groups/GardenProfessors Books: http://www.sustainablelandscapesandgardens.com

Cross-pollination making you cross?

No, your cucumbers have not hybridized with your melons.

I’ve been fielding different versions of the same question a LOT lately.
Three different people have sent pictures of “cucumelons” telling me they planted cucumbers next to their melons, and now the cucumbers look strange, so they’re concerned that they have cross pollinated with the melons. One person planted what was supposed to be a red raspberry next to their yellow raspberry, but the new plant is producing yellow fruit, so they think that it must be cross pollinating with their yellow plant, causing the fruits to turn yellow. Not to mention similar queries about tomatoes, peppers, and watermelons. It seems like every time a piece of produce turns out looking differently than what people expect, they blame pollen from the plant next to it.

I’m sure the highly educated readers of The Garden Professors know this already, but to clarify, there is a very simple reason why you don’t need to worry about one plant pollinating another plant and changing the quality of your produce UNLESS you are planning on saving seeds to grow for the next year.

When a flower is pollinated and starts developing into a fruit full of seeds, it is only the seeds themselves that combine the genetics of the two parents to develop into something new. Everything else – the flesh of a tomato, or cucumber or melon or raspberry – is produced solely by the mother plant, and the daddy of those seeds inside doesn’t matter a bit. Think about when a woman is pregnant… the identity of the father of the child inside her doesn’t change the character of the skin of her belly.

If you want to save seeds of your plant for next year, it is another matter, and you should be sure to isolate or (better yet) hand pollinate different varieties of the same species from each other to make sure they don’t hybridize unintentionally. You still don’t need to worry about your cucumbers and melons, however – they won’t hybridize by chance in your garden. If a plant doesn’t produce the right colored fruit or flower, most likely it was just mislabeled at the nursery. Grow a strange looking cucumber, chances are it was left on the plant too long. Cucumbers are harvested and eaten when young and immature, leave them too long and they get… strange looking. No need to blame it on the melons next to them.

There IS one exception to this, one common plant in the garden where the source of pollen makes a huge difference in what you harvest: Corn. Corn is the exception because what we’re eating is the seed itself, not the fruit produced by the mother plant surrounding the seed. That’s why if your sweet corn gets a dose of pollen from the field corn the farmer is grown next door, it comes out starchy and not sweet.

It also makes breeding colorful corn for fall decorations REALLY fun… Because when you see a multicolored ears of corn like this from my garden last year:

You can carefully pick out just the seeds showing the colors you like best, say the palest blues and pinks, sow them together the next year, and get something looking like this:

Or plant all the darkest kernels together and get this:

Plant sentience – “It is happening…again”

Those of you who were Twin Peaks fans will recognize the title quote. And while my topic is not quite as scary as being stalked by Bob, the fact that plant sentience continues to rear its irritating head in legitimate scientific venues makes me want to curl up in a ball and whimper. Here’s what made me cringe: “Sound Garden: Can Plants Actually Talk and Hear?”

I posted on this topic a few years ago, and I’d invite you to read it and the accompanying comments. I’m still not a fan of anthropomorphizing plants, and I still think word choices matter, especially when you are trying to educate people about science.

It’s disappointing that some scientists are deliberately using anthropomorphic language when discussing plant physiology. The cynical side of me says it’s a great way to get press coverage.

We’re watching you…

Bert, I’ll see your SOME-DED-TREES with POOR-DEAD-TREES

Bert’s done some nice posts on his SOcialME DesignED TREE transplant Study (or SOME DED TREES). I’m going to add to the discussion with a new addition to my Preventing Optimization Of Roots DecrEAseD TREE Survival (or POOR DEAD TREES) series.

It took a while, but the prediction I made in 2010 has come true. You’ll have to look at the link to see the whole story, but the bottom line is that this tree lasted only 7 years before succumbing to poor planting practices.

Here is the tree when it was planted in 2007. Note the lack of root flare (planted too deep) but the very obvious presence of orange nylon twine around the roots and the trunk.

Here it is again in 2010. Note the dieback at the top and overall chlorosis.

And here it was yesterday.

Yes, it’s dead – dead and gone. I’m not sure exactly when it was removed, but it lasted less than 7 years. Conifers have lifespans of decades or centuries. There was no excuse for this poor installation, though I keep getting the argument from landscape installers that it costs too much to do it right (i.e., to remove the twine and burlap, if not the clay itself). Keep in mind that warranties only last for a year, so the property owner gets to eat the replacement cost caused by crappy installation practices.

We GP’s may continue to disagree about how much rootballs should be disturbed when planting, but I know that none of us would agree that planting B&B trees intact is a good idea.

New publication on biodynamics

Happy New Year to our blog readers!

Now that we have our blog safely moved to this new format, we all resolve to post more frequently. (It’s actually Bert’s day to post, but given that his computer is probably frozen – literally – in Michigan, I’ll step in.)

Today I got a link to my most recent publication in HortTechnology on the science behind biodynamic preparations. I’ve written about this topic before, but recognize the importance of peer-reviewed information for researchers, extension educators, and Master Gardener volunteers. Not to mention all the gardeners who rely on us to provide good science for gardens and landscapes. So here it is. I’m planning to continue submitting review articles to HortTechnology on other topics of interest. It looks like permaculture might be the next one up.

So enjoy this article – pass it on to others who are curious about biodynamics, and if you are a Master Gardener be sure to take it to your MG coordinator and ask that it becomes a resource for your program.

Conventional vs. organic agriculture – the battle continues

An article was published earlier this week comparing the nutritional content of milk from organically raised cows to that from conventional dairies. The principle finding in this report is that “organic milk contained 25% less ω-6 fatty acids and 62% more ω-3 fatty acids than conventional milk, yielding a 2.5-fold higher ω-6/ω-3 ratio in conventional compared to organic milk (5.77 vs. 2.28).” (ω-3 fatty acids are considered to be “healthy” and you’ve probably heard of them in association with fish consumption.)

Of course, the popular press has had a field day with this, with such headlines as “Study finds organic milk is more nutritious.” This of course is nonsense, because the researchers didn’t study the health effects on people consuming the milk. But for argument’s sake, let’s assume this might be true and move on to the study itself.

What researchers actually found was that cows who feed primarily on pasture grasses and other forages (the “organic” cows) had elevated ω-3 fatty acids compared to those receiving a primarily grain-based diet (the “conventional” cows). This isn’t new information – other studies (such as this one) have consistently demonstrated this.

The problem with this newest paper is the inaccurate terminology used to describe the study. It really has nothing to do with whether the cows are raised organically or conventionally – it has to do with what they eat. A better experimental design would have included multiple comparisons among “organic” cows (who by default are grass-fed), “conventional” cows that are fed a grain diet (typical with large operations), and “conventional” cows that are pasture-raised (common with smaller farms that don’t want to jump through the organic certification hoops). I’m betting that the milk from this last group of cows wouldn’t be much different from the “organic” cows.

The upshot of using such imprecise terminology is that the message is lost amid the furor of the ongoing organic vs. conventional agriculture battle. Readers erroneously jump to a value-based conclusion – i.e., organic is “better” than conventional.

In my opinion, there’s no excuse for this. The experts who reviewed this article should have pointed out the loaded language and insisted on a change in terminology. (You might be interested to follow the comments on this article, one of which alludes to misleading terminology.)

Working out the bugs

It’s December and I hereby vow to post every week from now on! I’ve actually been on the blog behind the scenes for the last several weeks troubleshooting the archives. We transferred over four years of material from the old site, and there are still some rough patches. And that’s where you can help.

If you have been browsing the archives (listed on the right hand menu) or searching for topics (the search box is in the upper right corner just below the Garden Professors banner where the little magnifying glass lurks), you may have found odd line breaks, broken links, missing pictures, etc. in the posts and the comments. Or you might be searching for a particular post on the internet and end up with a 404 error page instead of the blog. It’s easy for me to fix these problems, but finding them takes some time.

So if you, our faithful readers, find these problems and post them below. We’ll have a contest: the top three contributors of bugs, breaks and boo-boos will each win a swell prize! (Not telling what the prizes are. You will have to wait and see.)

In the meantime, enjoy this photo of my husband Jim as we searched for the perfect Christmas tree last Friday.

How NOT to do an experiment

Over on Facebook I follow some groups who find provocative topics, and today’s “science fair” post was so over the top that I had to share it here.

Here’s the original post. Now the accompanying text about microwaves is whacky enough on its own (and well worth reading), but my primary interest is with the experiment. This exemplifies why there are basic rules for doing science.

This starts out okay – identical pots, the same type of media (I assume), similar sized plants – but then things go downhill:

1) Replicates are important. There is one treatment and one control, meaning that it’s impossible to run any kind of statistical analysis. Ideally between 10-20 replicates of the control and the experimental treatment are used in this kind of experiment. That’s 20-40 plants total.

2) Variable control is important. Plants in a windowsill are subject to light and temperature gradients. That makes analysis more complicated unless one has an extremely long windowsill so that all plants are treated uniformly. And then our researcher prunes the tops of the plants – yet another variable.

3) Consistency between treatments is important. It appears that the pot on the left is wetter than the one on the right – the media is darker. If it’s not draining well – for whatever reason – then you’ll have a hypoxic root environment. Plants don’t like that.

4) Objectivity is important. It’s difficult (impossible, really) for any researcher to be completely objective. Ideally, the pots would have been watered by another person and then labelled in such a way that the person recording the data would have no clue which was which.

I think it’s really important to get kids excited about science. But it’s just as important giving them guidelines about doing science in a way that advances their own understanding about how the world works. Otherwise, it’s just more fodder for the aluminum hat crowd.

Don’t worry…we’re still here!

I can’t even tell you how many months it’s been since I posted on the blog. It’s been a perfect storm for the four of us, with writing books (Linda), new jobs (Jeff), doing the Garden Professors gig in Toronto (Holly, Bert and Linda) and writing grant proposals (all of us). I am going to try my best to post once a week, even if it’s short and silly.

Something new to let you know…the blog will be moving to a new format in the near future. It will be a WordPress blog, which means it’s easier for us to post and easier for you to search. In theory, all of the old posts will migrate as well, along with the pictures and comments. We are all looking forward to a more user-friendly format.

In the meantime, take a look at the new portal to our WSU Gardening Webpage!

You can find the page by clicking here. We’re in the process of adding more material all the time, but you can be sure that whatever you find on this new page is relevant, peer-reviewed science for use by home gardeners.

Let us know what you think!

Container planting: intuition vs. reality

I’m just starting to think about getting my containers planted for the summer and happened to get an email on the topic from a blog reader. John was frustrated with a local columnist’s advice on using gravel in the bottom of the containers for drainage. When challenged, the columnist refuted John’s accurate comments with “logical thinking.” (You can find the posting and comments here.)

Here’s part of the post: “I like to cover the hole with a layer of gravel to improve drainage. Plants need to have their roots exposed to air in the soil to survive and thrive. If the container has no holes for drainage, it will fill with water and drown the plants very quickly. It is better to keep your plants on the drier side than to keep them constantly moist or wet. The big danger in using pots is drowning plants.” Later, he goes on to explain “The potting soil plugs up the drain hole and the water is trapped behind the plug. The layer of gravel creates an area for the water to drain through to escape. The creation of drainage commonly involves a layer of gravel.” This reasoning is part of what he calls “Logical thinking 101.”

As my husband pointed out, this isn’t logical thinking: it’s intuitive. It’s what we think is going to happen in the absence of any evidence. And in this case, it’s wildly inaccurate.

Jeff and I have both discussed the phenomenon of perched water tables in containers as well as the landscape in previous posts and on our Facebook page. The fact is, when water moving through a soil reaches a horizontal or vertical interface between different soil types, it stops moving. Here’s a photo from a very old research paper on the topic:

A layer of silt loam sits above a layer of sand, and water from an Erlenmeyer flask drips in. Intuition says that when the water reaches the sand, it will move more quickly through the sand because the pore spaces are larger than those in the silt loam. But intuition is wrong, as this series of photographs clearly demonstrate. Water is finally forced into the sand layer by gravitational pressure, after, of course, saturating the silt loam.

Intuition has its uses (I am quite proud of my own intuitive powers), but it doesn’t trump reality.

**This is an older post, so I’ve added this link to a peer-reviewed publication on the topic by Dr. Jim Downer and myself.**

Five little lavenders…four years later

If you’ve been following us for a while, you might remember a post from August 2009 when I got cranky about a pot of lavenders with horrendous root systems. I intervened with my Felcos and planted out the patients, hoping for the best.
Lavender #2 before root pruning

In July of 2010, I gave an update on their progress. At that point, one of the lavenders had died but the other four were perking along. And now it’s time to show them in their floral glory:

Root washing is still controversial, as is corrective root pruning. However, all five of these plants would have died had I not corrected the spiraling root systems. Published and ongoing research at several places around the country continues to support the practice of bare-rooting and correcting root flaws of woody plants.

Is this a practice that the landscape industry will adopt? Probably not on a large scale: it is time intensive and requires careful work. But home gardeners can do this themselves and have done so successfully.

If you’re interested in more information on how to do this, you can download this fact sheet. Until production nurseries change their practices to avoid these fatal root flaws, it will be up to home gardeners and a handful of landscapers to repair the damage.